Meta-Analysis
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Oncol. Jun 24, 2021; 12(6): 482-499
Published online Jun 24, 2021. doi: 10.5306/wjco.v12.i6.482
Phytochemically rich dietary components and the risk of colorectal cancer: A systematic review and meta-analysis of observational studies
Pia Borgas, Guadalupe Gonzalez, Kirill Veselkov, Reza Mirnezami
Pia Borgas, Faculty of Medical Sciences, University College London, London WC1E 6BT, United Kingdom
Guadalupe Gonzalez, Department of Computing, Imperial College London, London SW7 2RH, United Kingdom
Kirill Veselkov, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London SW7 2AZ, United Kingdom
Reza Mirnezami, Department of Colorectal Surgery, Royal Free Hospital, London NW3 2QG, United Kingdom
Author contributions: Borgas P performed the literature searching, study identification, data analysis and manuscript preparation; Gonzalez G performed data analysis and manuscript preparation; Veselkov K performed study inception, data analysis and manuscript preparation; Mirnezami R performed study inception, study identification, literature searching, data analysis and manuscript preparation; all authors have read and approved the final manuscript.
Conflict-of-interest statement: The authors declare no conflicts interests.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Reza Mirnezami, FRCS, MBBS, PhD, Senior Lecturer, Surgeon, Department of Colorectal Surgery, Royal Free Hospital, Pond Street, Hampstead, London NW3 2QG, United Kingdom. reza.mirnezami@nhs.net
Received: February 9, 2021
Peer-review started: February 9, 2021
First decision: March 31, 2021
Revised: April 6, 2021
Accepted: June 2, 2021
Article in press: June 2, 2021
Published online: June 24, 2021
Processing time: 131 Days and 10.1 Hours
Abstract
BACKGROUND

Personalized nutrition and protective diets and lifestyles represent a key cancer research priority. The association between consumption of specific dietary components and colorectal cancer (CRC) incidence has been evaluated by a number of population-based studies, which have identified certain food items as having protective potential, though the findings have been inconsistent. Herein we present a systematic review and meta-analysis on the potential protective role of five common phytochemically rich dietary components (nuts, cruciferous vegetables, citrus fruits, garlic and tomatoes) in reducing CRC risk.

AIM

To investigate the independent impact of increased intake of specific dietary constituents on CRC risk in the general population.

METHODS

Medline and Embase were systematically searched, from time of database inception to January 31, 2020, for observational studies reporting CRC incidence relative to intake of one or more of nuts, cruciferous vegetables, citrus fruits, garlic and/or tomatoes in the general population. Data were extracted by two independent reviewers and analyzed in accordance with the Meta-analysis of Observational Studies in Epidemiology (MOOSE) and Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) reporting guidelines and according to predefined inclusion/exclusion criteria. Effect sizes of studies were pooled using a random-effects model.

RESULTS

Forty-six studies were identified. CRC risk was significantly reduced in patients with higher vs lower consumption of cruciferous vegetables [odds ratio (OR) = 0.90; 95% confidence interval (CI): 0.85-0.95; P < 0.005], citrus fruits (OR = 0.90; 95%CI: 0.84-0.96; P < 0.005), garlic (OR = 0.83; 95%CI: 0.76-0.91; P < 0.005) and tomatoes (OR = 0.89; 95%CI: 0.84-0.95; P < 0.005). Subgroup analysis showed that this association sustained when looking at case-control studies alone, for all of these four food items, but no significant difference was found in analysis of cohort studies alone. Nut consumption exhibited a similar trend, but overall results were not significant (OR = 0.72; 95%CI: 0.50-1.03; P < 0.07; I2 = 90.70%). Putative anticarcinogenic mechanisms are proposed using gene-set enrichment analysis of gene/protein perturbations caused by active compounds within each food item.

CONCLUSION

Increased cruciferous vegetable, garlic, citrus fruit and tomato consumption are all inversely associated with CRC risk. These findings highlight the potential for developing precision nutrition strategies for CRC prevention.

Keywords: Colorectal cancer; Disease prevention; Diet; Risk; Nutrigenomics; Meta-analysis

Core Tip: Personalized nutrition and protective diets and lifestyles represent a key cancer research priority. Herein we present a systematic review and meta-analysis on the potential protective role of five common phytochemically rich dietary components (nuts, cruciferous vegetables, citrus fruits, garlic and tomatoes) in reducing colorectal cancer (CRC) risk. Results show that increased dietary consumption of cruciferous vegetables, citrus fruits, garlic and tomatoes is associated with reduced CRC risk. Active components of these may interact with certain genes to exert this anticarcinogenic effect, highlighting the potential for developing precision nutrition strategies for CRC prevention.